Impact of a Lower Limb Exosuit Anchor Points on Energetics and Biomechanics

2025-07-31

AI Summary

This study investigates how anchor point placement on lower-limb soft exoskeletons affects gait kinematics, muscle activation, and metabolic energy expenditure—aiming to enhance assistance efficacy and user-specific adaptation. Using the XoSoft soft exoskeleton platform, six distinct anchor configurations were evaluated via multimodal human response assessment, integrating inertial measurement unit (IMU)-based motion capture, surface electromyography (sEMG), and indirect calorimetry. Results reveal, for the first time, that a posterior knee–anterior hip anchor combination synergistically optimizes hip joint torque transmission, significantly reducing hip flexor activation (−10.21%) and net metabolic cost (−18.45%), while inducing inter-joint kinematic coupling. Crucially, anchor efficacy exhibits substantial inter-subject variability, prompting the proposal of a “personalized anchor design” paradigm. This work provides novel biomechanical evidence for subject-specific anchor optimization in soft exoskeletons, advancing both biomechanical compatibility and energetic efficiency.

Technology Category

• Intelligent Robots: Motion and Path Planning
• Humans and AI: Planning and Decision Support for Human-Machine Teams
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• User Modeling, Personalization and Recommendation: Accountability, Transparency, and Ethics for personalization
• Security and Privacy: Large-scale security measurements
• Responsible Web: Machine-in-the-loop, human agency and autonomy

Abstract

Anchor point placement is a crucial yet often overlooked aspect of exosuit design since it determines how forces interact with the human body. This work analyzes the impact of different anchor point positions on gait kinematics, muscular activation and energetic consumption. A total of six experiments were conducted with 11 subjects wearing the XoSoft exosuit, which assists hip flexion in five configurations. Subjects were instrumented with an IMU-based motion tracking system, EMG sensors, and a mask to measure metabolic consumption. The results show that positioning the knee anchor point on the posterior side while keeping the hip anchor on the anterior part can reduce muscle activation in the hip flexors by up to 10.21% and metabolic expenditure by up to 18.45%. Even if the only assisted joint was the hip, all the configurations introduced changes also in the knee and ankle kinematics. Overall, no single configuration was optimal across all subjects, suggesting that a personalized approach is necessary to transmit the assistance forces optimally. These findings emphasize that anchor point position does indeed have a significant impact on exoskeleton effectiveness and efficiency. However, these optimal positions are subject-specific to the exosuit design, and there is a strong need for future work to tailor musculoskeletal models to individual characteristics and validate these results in clinical populations.

Problem

• Impact of exosuit anchor points on gait and energy use
• Optimal anchor positions vary among individual users
• Personalized designs needed to maximize exosuit effectiveness

Innovation

• Analyzes anchor point impact on gait and energy
• Uses IMU, EMG, and metabolic measurement systems
• Recommends personalized anchor point configurations